New dog and fighting

[bullseye]

I have a 5yo male desexed neo mastiff x bandog who has been the only dog in the house for 4 years, Just today picked up a female unspade 11month neo mastiff. The male is great with my friends dogs and play quite happily with them and even had a sleep over with one and nothing even was close to being uncomfortable, was like they were brother and sister. The female has come from a group of 5 other female pig hunting dogs and I think did not get much human attention. The introduction went well, let the female into the yard and sniff her way around the place, let the male out both smelt each other for sometime and the hackles were up on both but no growling and ears back, after sometime they were still a little weary of each other but ok. Took them both for a walk on a lead and both were great. When home both tired and were happy to lay down next to each other.
The male is an inside dog and the female I suspect has never been allowed inside, so we then blocked the hallway off and allowed both dogs to be in the garage together, which was fine. Feeding was a little tense and was at either end of the outside area and supervised. Later tonight went to check on them in the garage and was well, we went outside the male wanted to play so we started to play a little, which was also good as the female wanted to play as well. They stood off each other as if they wanted to play with each other but were not sure. A little play together and my partner and I were smiling thinking this will work out. Wrong. Male grabbed the rope he likes and then female got the other end, playing then turned into growling, the female let go and started to walk away and the male then went for her, fight started, hose used fight ended both a little bloody female crying and wanting attention from us and the male still aggressive. Now, female is outside male inside for the night.
I should also state that I think the female is not very well trained as in sit and drop, but seems submissive, and is food motivated.
So we would like any help and ideas to make our family a happy 1, and would dearly love to keep the female as she seems to have a beautiful nature when by herself.